As disclosed in U.S. Pat. No. 3,748,320 (Vorbruggen et al., it is known that pyrimidine nucleosides are useful in the pharmaceutical industry and that they can be prepared by reacting a suitable pyrimidine with a protected 1-halo, 1-alkoxy, or 1-acyloxy sugar in the presence of tin tetrachloride, titanium tetrachloride, zinc chloride, boron trifluoride, aluminum chloride, or ferric chloride as a catalyst. This process has been found to be very satisfactory for preparing biologically-active nucleosides from sugars having a 2-hydroxy group. However, it is less satisfactory for preparing nucleosides from 2-deoxy sugars. When a 2-deoxy sugar derivative is used as a starting material in the process of Vorbruggen et al., the amount of the biologicallyinactive alpha-anomer formed is substantial, and the yield of the desired beta-anomer is accordingly decreased. In fact, it appears that the best beta-anomer/alpha-anomer ratio that can be obtained when a 2-deoxy sugar derivative is used in the process is only about 60/40. It would be advantageous to be able to increase this ratio.